Defiagbon was an accomplished Nigerian and Canadian amateur boxer, winning 180 matches with only 20 defeats.

He won the Commonwealth Games in 1990.

Defiagbon was a Nigerian and All-African champion. He competed for Nigeria in the 1992 Olympic Games in Barcelona, losing in the first round of the light middleweight division to future world champion Raul Marquez.

He fled his native Nigeria in 1992 for what he calls "political" reasons. He went to Canada and obtained Canadian citizenship ...he won the Canadian heavyweight title in 1996.

He finished first at the Olympic Trials in 1996 in San Juan, Puerto Rico and first again at Thunder Bay, Canada, the same year.

In Atlanta Olympic Games in 1996, Defiagbon, the heavyweight who left Nigeria for Halifax, had his hand raised in victory, assuring him of at least a bronze medal, a medal won by disqualification.

An apparent low blow thrown by Christophe Mendy of France in the third round sent Defiagbon reeling to the canvas in severe pain. And after a doctor examined Defiagbon in the ring and took the Canadian's word that he couldn't continue, Mendy was disqualified. The fight was stopped. Several minutes later, referee Abduk Samad disqualified Mendy and the Canadian advanced in the heavyweight division. In semi-final, he won on Nate Jones (USA) 16-10. He took the silver medal losing a decision 2-20 to Felix Savon of Cuba in the final.